Method of electroforming containers having openings with thick sections at the openings

ABSTRACT

D R A W I N G A METHOD OF ELECTROFORMING A CONTAINER HAVING A THICKENED SECTION AT AN OPENING IS PROVIDED. A CATHODIC ELECTRODE SURFACE IS APPLIED ON THE ENTIRE AREA OF AN EXPENDABLE MANDREL EXCEPT FOR AN AREA AT WHICH AN OPENING IS TO BE PROVIDED. THE MANDREL IS THEN PLACED IN A BATH OF ELECTRICALLY CONDUCTIVE SOLUTION. SEPARATE POWER SOURCES ARE APPLIED TO A PLURALITY OF ANODES. ON E OF THE ANODES IS DISPOSED RELATIVELY CLOSE TO THE AREA AT WHICH AN OPENING IS TO BE FORMED THEREBY PROVIDING A RELATIVELY THICKENED PORTION OF ELECTRODEPOSITED MATERIAL WITH RESPECT TO THE MATERIAL DEPOSITED ON THE MAIN SURFACE OF THE MANDREL.

1971 M. MATTIA METHOD OF ELECTRQFORMING CONTAINERS HAVING OPENINGS WITH THICK SECTIONS AT THE OPENINGS Filed May 1, 1968 WW I HH I IW IOM II U I II I II I I M HH H |II|M I II I I I H M JI H IH H mm I IIII| IIIIh IIII II In II I I I II I I I o II INVENTOR.

MICHAEL MATTIA- ATTORNEY United States Patent 3,560,349 METHOD OF ELECTROFORMING CONTAINERS HAVING OPENINGS WITH THICK SECTIONS AT THE OPENINGS Michael Mattia, Upper Darby, Pa., assignor to The Budd Company, Philadelphia, Pa., a corporation of Pennsyl- Vania Filed May 1, 1968, Ser. No. 725,765

Int. Cl. (12% 7/02; B01k 3/02 US. Cl. 2049 4 Claims ABSTRACT OF THE DISCLOSURE A method of electroforming a container having a thickened section at an opening is provided. A cathodic electrode surface is applied on the entire area of an expendable mandrel except for an area at which an opening is to be provided. The mandrel is then placed in a bath of electrically conductive solution. Separate power sources are applied to a plurality of anodes. One of the anodes is disposed relatively close to the area at which an opening is to be formed thereby providing a relatively thickened portion of electrodeposited material with respect to the material deposited on the main Surface of the mandrel.

As is well known, electroplating is the process of coating an article with a thin layer of a metal through electolytic deposition. The article to be plated is generally immersed in an electrolytic bath and becomes the cathode in the electrolytic system. Also immersed in the bath is an anode composed of the plating metal. A voltage is applied between the cathode and the anode causing a current to pass through the electrolytic solution, which electrolizes and plates the cathode with the anode material to tht desired thickness. In this way articles may be plated with silver, copper, iron, cadmium, nickel, and a variety of other metals.

The use of electroforming to make articles such as dies and molds has a number of advantages. In many cases, dies and molds made by conventional methods are very costly. Lower cost and shorter delivery schedules are possible when electroforming techniques are used in place of conventional machining methods. This is especially true if the shape of the mold or die is of an unusual shape.

One example of a mold which may be made by electroforming, to which the invention of this application relates involves a mold to be used for rotational casting of plastic articles, for example. In this case the plastic may be put into the mold while in a liquid condition. A cap or cover is attached to close the opening in the mold. The mold is then mechanically attached to a driving means including a motor. The mold is then rotated and heated and a thin coating of plastic is formed on the walls of the mold. After the plastic has hardened and cooled, the cap is removed from the thickened portion of the mold. The plastic hollow article formed may then be collapsed and taken out of the mold. The hollow article may then be filled with suitable material to form the article being manufactured, For example, a headrest for an automobile may be made by such a process.

In making such a mold, it is necessary to have an opening therein to permit the hollow plastic article formed to be taken out of the mold. As mentioned, it is necessary to attach the mold to a suitable mechanical means for rotation. In this case, it is necessary to close the opening in the mold with a cap. The portion of the mold attached to the cap or cover should be relatively thick and strong enough to permit the mechanical connection.

It is an object of this invention to provide an improved metal mold.

"ice

It is a further object of this invention to provide an improved metal mold which may be used for rotational casting hollow plastic articles.

It is still a further object of this invention to provide an improved metal mold for rotational casting which has reinforced sections to permit the mold to be mechanically attached to other elements.

In accordance with the present invention, a method of electroforming containers is provided. A mandrel for receiving the metal to be electrodeposited includes a conductive surface which is made the cathode except for a small area at which an opening is to be provided. A plurality of anodes are spaced different distances about the mandrel. The mandrel is immersed in a bath of electrically conductive solution. The anodes are connected to separate power sources. One of the anodes is disposed relatively close to the area at which the opening is to be. This permits deposition of relatively thick metal about the opening with respect to metal deposit on the remainder of the mandrel. After the mold is formed, the mandrel body is removed by dissolving, heating, mechanical extraction or by other suitable methods. The thickened portion at the opening permits the mold to be mechanically attached to a cap or cover and subsequent rotational casting.

Other objects and advantages of the present invention will be apparent and suggest themselves to those skilled in the art, from a reading of the following specification and claims, in conjunction with the accompanying drawing, in which the sole figure of the drawing illustrates a method and means for making a metal mold.

Referring to the drawing, a mandrel 10 is immersed in a conventional nickel plating solution 12. A plurality of anodes 14, 16 and 18 are also immersed in the solu tion 12. The main body of the mandrel may be of a suitable resin or other type material which may be melted or otherwise disposed of after the mold has been formed. The mandrel may include a thin coating of silver 20 which may act as a cathode in the electrodeposition process. The mandrel may be irregular in shape, as indicated, and designed to produce a mold having an opening toward the top.

The mandrel 10 is held by a rod 22 which extends into the mandrel and may be held by a bar 24 which is made of conductive material. The rod 22 is also composed of conductive material and is adapted to be connected to the negative side of a battery 36 through the bar 24. The rod 22 extends through an insulated element 26, the auxiliary anode 18, an insulated element or spacer 28 and a thin metal sheet element 30. A space 32 is provided between a rod 22 and the anode 18 to prevent any electrical contact therebetween. The element 30 provides an electrically conductive path between the coating 20 and the rod 22.

The anodes 14 and 16, which are illustrated as bars but which may be any suitable shape, are suitably connected to the positive terminal of a battery 34. The anode 18 is connected to the positive terminal of the battery 36. The battery 36 may be associated with a potentiometer 37 for varying the voltage applied to the anode 18, as indicated by the arrow. Such means for varying may include a potentiometer or other suitable well known means not illustrated.

The process of depositing the metal on the mandrel is carried out in a conventional manner. However, it is noted that the auxiliary anode 18 is fastened in close proximity to the mandrel rather than being spaced at a distance as is the case of the anodes 14 and 16. This arrangement permits the current fiow from the auxiliary anode 18 to be concentrated around the opening to be formed in the mold thereby producing a thicker deposit in this area.

It is noted that the deposit of nickel 38 about the main surface of the mandrel is relatively uniform and thin. However, the nickel plating 4.0 surrounding the opening to be formed in the mandrel is relatively thick because of the position of the auxiliary anode 18.

Separate power sources are provided for the anodes 14 and 16 and the anode 18. Because of the separate power supplies and the fact that one is variable with respect to the other, the amount of relative thickness surrounding the opening of the mold with respect to the main surface may be controlled by varying the voltage from the battery 36.

After the electrodeposition process has been completed, the mandrel with its coated metal is taken out of the solution. The insulated element 26, plastic spacer 28 and metal sheet element 30 are then removed from the mandrel. The resin or other material making up the mandrel is then dissolved leaving the nickel plated container having an opening therein. The relatively thick portion at the opening permits the mold to be suitably attached to a mechanical arrangement to permit rotation thereof.

In a practical operation, liquid plastic or other such type material may be inserted into the mold which is rotated. A coating is formed on the walls of the mold. After the coating has hardened, the mold is removed from the mechanical connection and the plastic bag or article is collapsed and taken out of the mold. The plastic article may then be filled with suitable material and used as a headrest or other article.

In one embodiment of the invention the nickel solution bath may include nickel sulfamate [Ni(NH SO nickel chloride (NiCl '6H O), boric acid (H BO and suitable wetting agent.

Suggested operated conditions may comprise a pH (electrometric) between 3.84.0, the temperature may be 49 degrees centigrade; the current density may be between 50 amperes per square foot, and the anodes may be sulfur depolarized or rolled depolarized nickel.

What is claimed is:

1. A method of electroforming containers having a thickened section at an opening comprising the steps of providing a mandrel to receive metal to be electrodeposited, coating a cathodic electrode on the entire surface of said mandrel except for an area at Which said opening is to be provided, placing an electrically conductive member on said mandrel at the area at which said opening is to be provided, providing a main anode, providing an assembly including an auxiliary anode with insulated members disposed on either side thereof whereby only the outer edge of said auxiliary anode is exposed, placing said assembly on said electrically conductive member with the outer edge of said auxiliary anode in close proximity to the area at which said opening is to be formed, immersing said mandrel with said assembly and said main anode in said electrically conductive solution, applying voltages from separate power sources to said main and auxiliary anodes to cause current to flow in different paths in said solution and metal to be deposited on said mandrel with said auxiliary anode causing deposition of relatively thick metal about said area with respect to the deposition of metal on the main surface of said mandrel.

2. The invention as set forth in claim 1 wherein the voltage from the power source connected to said auxiliary anode is variable to permit different thicknesses of metal deposits to be formed about said opening.

3. The invention as set forth in claim 4 wherein the additional step is provided of placing said metallic element in physical contact with said mandrel to provide an electrically conductive path between said anodes and said cathodic element.

4. The invention as set forth in claim 3 wherein the additional steps are provided of providing apertures in the auxiliary anode and insulated members of said assembly with the aperture of said auxiliary anode being larger than the apertures in said insulated members, and passing a conductive rod through said apertures of said auxiliary anode and insulated members to electrically connect said electrically conductive member to a return point on said power sources.

References Cited UNITED STATES PATENTS 895,164 8/1908 Cowper-Coles 204-9 1,526,644 2/1925 Pinney 204-231 2,044,431 6/1936 Harrison 204231 FOREIGN PATENTS 23,679 1894 Great Britain 2049 JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner US. Cl. X.R. 204231 

